Your network contains an Active Directory domain named contoso.com. The domain contains the  servers shown in the following table：    
Server name  Operating system  Role  
DC1  Windows Server 2008  Domain controller  DC2  Windows Server 2008 R2  Domain controller  DNS1  Windows Server 2008  DNS server  DNS2  Windows Server 2008 R2  DNS server    
The functional level of the forest is Windows Server 2003. The functional level of the domain is  Windows Server 2003.  
DNS1 and DNS2 host the contoso.com zone. All client computers run Windows 7 Enterprise.    
You need to ensure that all of the names in the contoso.com zone are secured by using  DNSSEC.  
What should you do first（）

Your company has a main office and a branch office.    
The network contains an Active Directory domain named contoso.com. The DNS zone for  contoso.com is configured as an Active Directory-integrated zone and is replicated to all domain  controllers in the domain.  
The main office contains a writable domain controller named DC1. The branch office contains a  read- only domain controller （RODC） named RODC1. All domain controllers run Windows Server  
2008 R2 and are configured as DNS servers.    
You uninstall the DNS server role from RODC1. You need to prevent DNS records from  replicating to RODC1.    
What should you do（）